/* Turn Lab to LCh
 *
 * 2/11/09
 * 	- gtkdoc
 * 	- cleanups
 * 18/9/12
 * 	- redone as a class
 */

/*

	This file is part of VIPS.

	VIPS is free software; you can redistribute it and/or modify
	it under the terms of the GNU Lesser General Public License as published by
	the Free Software Foundation; either version 2 of the License, or
	(at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU Lesser General Public License for more details.

	You should have received a copy of the GNU Lesser General Public License
	along with this program; if not, write to the Free Software
	Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
	02110-1301  USA

 */

/*

	These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk

 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /*HAVE_CONFIG_H*/
#include <glib/gi18n-lib.h>

#include <stdio.h>
#include <math.h>

#include <vips/vips.h>

#include "pcolour.h"

typedef VipsColourTransform VipsLab2LCh;
typedef VipsColourTransformClass VipsLab2LChClass;

G_DEFINE_TYPE(VipsLab2LCh, vips_Lab2LCh, VIPS_TYPE_COLOUR_TRANSFORM);

/**
 * vips_col_ab2h:
 * @a: CIE a
 * @b: CIE b
 *
 * Returns: Hue (degrees)
 */
double
vips_col_ab2h(double a, double b)
{
	double h;

	/* We have to get the right quadrant!
	 */
	if (a == 0) {
		if (b < 0.0)
			h = 270;
		else if (b == 0.0)
			h = 0;
		else
			h = 90;
	}
	else {
		double t = atan(b / a);

		if (a > 0.0)
			if (b < 0.0)
				h = VIPS_DEG(t + VIPS_PI * 2.0);
			else
				h = VIPS_DEG(t);
		else
			h = VIPS_DEG(t + VIPS_PI);
	}

	return h;
}

void
vips_col_ab2Ch(float a, float b, float *C, float *h)
{
	*h = vips_col_ab2h(a, b);
	*C = hypot(a, b);
}

static void
vips_Lab2LCh_line(VipsColour *colour, VipsPel *out, VipsPel **in, int width)
{
	float *restrict p = (float *) in[0];
	float *restrict q = (float *) out;

	int x;

	for (x = 0; x < width; x++) {
		float L = p[0];
		float a = p[1];
		float b = p[2];
		float C, h;

		p += 3;

		C = sqrt(a * a + b * b);
		h = vips_col_ab2h(a, b);

		q[0] = L;
		q[1] = C;
		q[2] = h;

		q += 3;
	}
}

static void
vips_Lab2LCh_class_init(VipsLab2LChClass *class)
{
	VipsObjectClass *object_class = (VipsObjectClass *) class;
	VipsColourClass *colour_class = VIPS_COLOUR_CLASS(class);

	object_class->nickname = "Lab2LCh";
	object_class->description = _("transform Lab to LCh");

	colour_class->process_line = vips_Lab2LCh_line;
}

static void
vips_Lab2LCh_init(VipsLab2LCh *Lab2LCh)
{
	VipsColour *colour = VIPS_COLOUR(Lab2LCh);

	colour->interpretation = VIPS_INTERPRETATION_LCH;
}

/**
 * vips_Lab2LCh: (method)
 * @in: input image
 * @out: (out): output image
 * @...: %NULL-terminated list of optional named arguments
 *
 * Turn Lab to LCh.
 *
 * Returns: 0 on success, -1 on error
 */
int
vips_Lab2LCh(VipsImage *in, VipsImage **out, ...)
{
	va_list ap;
	int result;

	va_start(ap, out);
	result = vips_call_split("Lab2LCh", ap, in, out);
	va_end(ap);

	return result;
}
